LO can't pass gas or poop. Help?

So we just switched our LO over to Similac Sensitive about a week ago. She was doing fine with pooping and gas. Seemed like she was doing a lot better than when we had her on Similac Advanced. Anyways, the last two days she has had really bad gas. She had one big poop over 24 hours ago, but nothing since. You can tell she's bloated and either trying to pass gas or have a bowel movement. She's been super fussy for the last three hours and trying to push something out. I've tried everything. Gripe water, bicycle kicks, tummy time, rectal thermometer and nothing has worked 😫 I feel so bad. Any suggestions?
**Edit: she is 3.5 weeks old